Circuit breaker latch



w uwi y 3 1 0 R. w. THOMAS 2,938,983.

CIRCUIT BREAKER LATCH Filed Aug. 1, 1958 4 Sheets-Sheet 1 INVENTOR.

ROB ER T W. THOMAS ATTORNEYS May 31, 1960 4 R. w. THOMAS 2,938,983

CIRCUIT BREAKER LATCH Filed Aug. 1, 1958 4 Sheets-Sheet 2 Y 37 22 o LEE. IL-J r e F lo 53 L 1 7s 52 58 I4 i 44 5 48 6* i I 50 F 56 IIIIIHIIT I :11!

22 Flag; 4 26 23 INVENTOR.

ROBERT W. THOMAS BY W% MZW ATTORNEYS May 31, 196!) R. w. THOMAS cmpun BREAKER LATCH Filed Aug. 1, 1958 4 Sheets-Sheet 4 INVENTOR ROB ERT W THOMAS fifl M 6 ATTORNEYS .States Patent cmom BREAKER LATCH- Filed Aug. 1, 195a,- sin. No. 152,630

8. Claims. ci; .2itiii-116 'I-he instant invention relates to electric switches and is particularly directed to means for obtaining a predetermi'n'ed automatic typesetting: for a switch of the type described in'the Elwood Platz Patent 2,3 85,727.

In the switch of the above identified patent a single niai n spring is utilized toflprovide the forces for snapa'ctionopening and closing of the switch contacts and also provides the pressure for a releasable latch which comprisesa bimetallic element whose deflection is efiectiveg-tof cause release of the latch.

i'lihe' main: spring at one end bears against the switch casing and the other end against the contact arm upon which the movable contact is mounted and which also carries the bimetallic element. The line of action of the spring is such asto produce a component of force which returns: the latching portion of the bimetal to its proper c'ool position when the switch is turned On. This same component of force holds the contact arm in a reference position against a cam plate while the bimetal deflects because of heating and cooling in its normal functional operation.

It has been found that for the large main springs required of high capacity switches, the increased. spring forces tend-to tilt the contact arm so that the latching position of the bimetal becomesunpredictable. In order to obtain a stable. and reproducible latch distance, the main springmust be made to assume a shape or position such as, to provide-an additional force or pressure at the back, end of the contact arm.

This is: accomplished; byproviding the. end of the casing wjith aninclined'sejat. Thuslthe spring-is caused to buckle the contaqtzarm and exert a component of force in meprcner direction? at the backendthereof.

;-;-..Ac.cor ly,; a primary object of-the instant invention isvto nr vide' novel means: wh re y p dictable latch bite of a bimetallic element may be obtained.

AnQ hQrbieQtstopra ide means h r y t main sp ingct an el c 'eswiteh utilized to stabilize' p sit onsp th ts tt empcn nts.

S ill'aaethereh o p o d a s op ng. a for onen o a'-c0 -1-typ main' p in h by th sp i huckled c xerta t m c mp n nt directed to urge the moyablev contact carrying arm against the switch asingi. 1 1 H These as well as other objects of the instant invention shall become readily apparent after reading'the following description of: the. aQQQmpanying; drawings in which:

.F igure'1gis--a perspective view of an electricswitch. Figures 2-4. are-front elevations with the front of the casing removed; showing the elements of the switch. In Figures 2-.and- S the elements are'in the OE and On posi- QBSr respectivelnwhile-in" Figure 4 the elements are shown;atrtheend-ofan inward stroke of the handle after the. elements are in the olfposition.

Figures and '6i ar'e'perspective viewsof the operating handle F Figure "7. is a perspctiveview of the casing.-

2,938,983 Patented May 31, 1960 Figure 8 illustrates the switch elements separated from one another.

Figures 9-11 are vertical cross-sections taken through planes at right angles to the front elevations of Figures 2-4. Figures 10 and 11 illustrate the manual latch releasing action.

Figure 12 is a horizontal cross-section of the switch.

Figures 13 and 14 are perspective views showing the indicator in} the On and Oil? positions respectively.

Figure 15' is a perspective viewof the switch elements mounted in the casing with' the switch in the On position.

Figure 16 is a-frag'mentaryhoi'izontal cross-section of the switch illustrating-the latching position of the bimetal tip.

Figure 17 is a perspective view of a wedge shaped insert which serves as a seat-for the main spring.

The drawings show the switch as comprising a cup shaped casing 10 having an openfront closed by a plate or cover 11 secured thereto, as by screws (not shown). The back of the case is formed with two openings, 12 and 13, for line and load terminals 14-15.

In an opening l6 reciprocates a handle or actuator 17 formed as a push button. A groove 18 of the handle receives a tongue 19 of the casing, with operating clearancesprovided between the. side walls 2021 of the handle and the left and right side surfaces 22 and 23 of the casing interior; the back and front surfaces 24--25 of the handle slidably engage the back surface 26 of the casing and the surface of the cover.

A cross ledge 28 of the casing has at 30,;a seat for a coiled compression spring 31 which biases the handle outwardly, the upper end of the spring seating in a socket 32 of the handle back, and against a lug 33 thereof, which lug is adapted to cooperate with the upper end of a spring receiving socket in the back' of the casing to limit outward motion of the handle; another limitation or stop for handle movement is provided by a handle lug 34 formed for cooperation with a pawl 35; still another limitation or stop for handle movement is provided by a handle lug 36 formed to cooperate with a casing lug 37.

The pawl 35, later to be described in detail, restrains outward travel of the handle, but only during the closed circuit position, merely holding the handle in an intermediate or on position, and preventing the handle from going all the way out to its open circuitor off position.

Handle. position is relied upon to indicate the position of the circuit closing parts within the casing. The handle is furthest out in the open circuit or oif position; it is held by the pawl 35, not so far out in its circuit closed or on position; when the handle is pressed down from the, closed circuit position for opening the circuit, it travels into the. case a slight distance so as to release itself from the pawl 35 above mentioned, whereupon the spring 31 moves the handle well out of the casing to the o position, movement being stopped by parts 36-37.

Movement of the handle is utilized to operate an indicator in the form of a plate 38 having an actuating lug 40 and having on and off markings. The plate is disposed within an undercut portion 41 of the handle so. that only one of the two markings of the plate is visible at any time through a window slot 42 of the handle. The lug 40 ridesin .a camminggroove 43 formed in the upper portion of the back of the casing.

As the handle moves up and down, the plate 38 moves, back and forth alternately in the undercut 41 to expose. its on and oh markings alternately to view through the slot 42. When the handle is full out or in the off position, the lug 49 of theindicator plate 38 is in the upper or back part of the groove 43 and the o marking is exposed through slot 42. As the handle is moved down, plate 38 slides down with the handle and foraasaass ward of the slot 42 to present its on marking to slot 42. In the on" position of the handle, lug 40 of plate 38 is in that part of groove 43 which causes plate 38 to have its on marking exposed at slot 42; and only when the handle is in the extreme out or off position will the lug 40 be in the upper or rear-most part of groove 43 so that the off marking of plate 38 is exposed to slot 42.

Since the handle occupies but one circuit open position, whether the circuit be opened manually or by auto matic overload release, the handle has but two rest positions, on and off, and these two positions indicate the conditions of the circuit controlling parts of the breaker.

The circuit controlling parts of the switch includea stationary contact 44 disposed under and against a ledge 45 of the casing and formed integral with line terminal 14. A U-shaped fibre arc shield 46 engages a hooked stop lug 47 of the casing. Adapted to make butt contact with the stationary contact 44 is the contact portion 48 of a movable contactor 49 having an L-shaped contact arm 50 which is riveted at 51 to a bimetal strip 52, with rivet 51 being formed as a pin to provide a loose pivotal connection between the contactor 49, comprising parts 50-52, and a cam plate 53 of insulation, the latter having an elongated slot 54 receiving a stop lug 55 formed on the back of the casing. Pawl 35 is an integral part of plate 53.

An operating spring 56 has its lower end in a seat 57 of the casing and its upper end surrounding a spring lug 58 formed from the contact arm 50. Spring 56 functions to rotate arm 50 counter-clockwise for circuit opening on the axis of pivot pin 51 when the latching hook 60 forming the free end of the bimetal strip 52 is released from engagement with the holding .abutment, i.e., the latching edge 61 of the plate 53. Such release of latch 60 from the holding means 61 is effected either automatically, by the warping of the bimetal 52 on overload, or manually, by the camming action provided by a sloping cam 62 of and integral with the handle. When this cam is pushed down it cams latch hook 60 oif the abutment or holding means 61, to permit the contact arm to be rocked counter-clockwise relative to the plate 53 by the spring 56, for circuit opening.

Spring 56 also biases contactor t) and plate 53 upwardly, and when the latch holds, provides the force to move contact 48 towards and press contact 48 against contact 44.

In a circuit opening action (Figures 2-3), spring 56, through pivot axis 51, will slide the plate 53 upwardly, with the latter guided by the casing; the engagement of the lower edge of plate slot 54 with casing stop 55 will limit such movement of the plate. That stop 55 will at that time function as a pivot for the plate 53 and since the line of action of spring 56, through axis 51, is to the left of that pivot, plate 53 will rock clockwise about stop 55, under the spring biasing force (Figure 2). Pawl portion 35 of plate 53, which normally holds handle 17 against extreme outward movement, will thereupon be caused to release its hold on lug 34 of handle 17 to release that handle and permit it to travel to the full off position, under the bias of spring 31.

In the on position, however, that plate 53 is so positioned by the spring 56 and by the casing walls that pawl 35 engages handle lug 34 to hold the handle against full outward travel to off position.

A flexible connector 65, looped around the bimetal strip 52, has one end 66 secured to the free end of that bimetal strip and has its other end 67 secured to that part of the load terminal 15 that was thrust intothe casing through the load terminal hole 13. This connector completes the circuit between the two terminals 14-15, employing only that part of the contact arm 50 extending from contact 48 to pivot pin 51 for carrying current.

The end of pivot pin 51 near the back of the casing is seated within a casing pocket 68, elongated to permit the pin 51 to slide up and down.

A lug 70 bent down from terminal 15, is the part to which the end 67 of connector 65 is secured.

To restore the parts to the circuit closing position (Figure 3), the handle 17 is pushed down as far as it will go and it will go down far enough, first to cause the notch 71 of a cam part thereof to engage a resetting lug 72 of the plate 53, and second, to cause the pin 51 to slide downwardly. That part of plate 53 connecting lug 72 and pin 51 acts as a translator. The contactor 49 will move downwardly with pin 51 until arm 50 reaches a resetting stop 47 of the casing, although in many instances that stop will have been engaged by the arm 50 at the end of the circuit opening movement of the arm. Continued downward movement of the handle and continued downward movement of the lug 72, and pin 51, will cause the contactor to engage stop 47 and rock clockwise, on axis 51, far enough to cause latch 60 to slide over or overtravel beyond holding edge 61 (Figure 4), for relatching. The release of the handle by the operator at that time will free the handle to be moved to its outward position by the spring 31 (Figure 3), and as the handle moves outwardly, the spring 56 will act on the contactor.

The contactor will rock slightly counterclockwise and assume its final on position, with latch 60 engaging holding edge 61, and with contact 48 abutting contact 44 under pressure of spring 56. Plate 53 will rock counterclockwise to place lug 72 out of the path of cam 71.

The space 74 between ledge 28 and the line terminal ledge 45 provides a pocket for the flexible connector 65, which, thus being pocketed, is restrained from fouling the moving parts of the device to impede their operation.

At 75 is illustrated a calibrating tip of the contactor, engaging the plate 53, and determining the position of the latch tip 69 relative to the latch surface 61.

When the contactor is manufactured, the position of the flexible tip 60 relative to rigid tip 75 may not be moved for calibration and to obtain an accurate positioning of tip 60 with respect to tip 75; since the position of rigid tip 75, formed to engage the edge of plate 53, is not variable, calibration of the position of tip 60 relative to tip 75 automatically insures calibration of the position of tip 60 relative to plate 53 and automatically insures calibration of the amount of overlap of tip 60 on edge 61 of plate 53 and automatically insures calibration of the amount of warping of tip 60 from edge 61 of plate 53 that is required to unlatch the breaker.

In switches adapted for low current capacity the switch construction as heretofore described is quite satisfactory.

In order to provide a force component for latching contactor 49 to cam plate 53, the force line of action of main spring 56 is tilted downward toward lug 58 of contactor 49, from the case 10. With relatively light springs, this force component is sufiicient to provide the latching action required but not enough to upset the stability of contact arm 50 which is supported by case formations 55 and 98. To further facilitate this stability, a hold down spring 96 may be positioned around rivet 51 to bear against case 10 and contact arm 50. However, the force of spring 96 must be maintained at a low value since this force also increases the frictional sliding com ponents between contactor 49 and the surfaces of the casing 10 and cam plate 53 upon which contactor 49 bears when the switch is tripped Off and latched On.

For higher capacity switches, stronger main springs are required with the latching force component thereof tending to upset the stability of contact arm 50 in a manner which causes the portion of contact arm 50 to lift or tilt away from case formation 55. The remaining two points of support at case formation 98 and tip 75 eateries oftcontactaarm. sll cfeate a pivot. line about, which 9 W lli-m Th ai th tw n at 95- lifts or tilts upward withrespect to Figure 15, the hi metal latch; tip- 60, beingmechanicallytied tofcontact arm dB-and, being omtheq opposite side of pivotline 97, will tilt downward. tilteauses anrundesirable and variable increase in-the bitesof the bimetal; latch; tip 60. g

In order .to maintain the stability ofcontact arm: 50, main, ,spring '56 is; shaped or. distorted so astoexerta component of; force-upon contact. 50 which urges portion 95 thereof toward; cam Plate. 53.v This is accomd h rtb ha ina o e dpf m n sa ne 6 ea e o sloping formation90- (:Figure l5) formed. integrally with case 1 ;which.lcauses, main spring 56 to -buckle againstcontactarm 5 :0- and urge portion: 95 against case formation 55]. U y p 4 Instead ofp't g anrintegrally formed sloping; seat 90,; a wedge shaped; insert 89: {Eigure 17)" may bepiaced in. case recess 57; gFigure 7-) which provided alevel seat for main spring 56.

With. this construction. latch tip; 60, will. always assume a predetermined position with respect to latch surface 61v o-f'cam. plate 53.

Although; I have here? described preferred embodiment of my novet, invention, many variations and modifications will, now be; apparent to those skilled in the art, and I therefore; prefer to be limited, not by the specific disclosure herein, but only by the appending claims.

1'. An: electric switch comprising a casing, a cam plate,; a eontacton; an operating handle; and a main springsaid cam: plate, said contactor, and said main spring being disposed-within said casing; a fixed contact secured to said casing anda movable: contact carried by said contactor and engageable with. said fixed contact; said; contactor being operatively connected to said cam plate;- said handle: being enga-geable with said cam plate for movement of saidcontactor and. said cam plate to positions wherein said main spring is effective to latch said contactor to said cam plate and to bring said contacts into engagement; said handle being engageable with saidcontactor for movement thereof to; a position wherein a ma n latiue fifi tiv to bring ut t d engagement of said contacts seating means for said. main spring constructed and positioned whereby said main spring is positioned to exert a component of force urging said contactor toward said cam plate to assume a predeterminable position with respect thereto when said contactor is latched to said cam plate.

2. An electric switch comprising a casing, a cam plate, a contactor, an operating handle, and a main spring; said cam plate, said contactor, and said main spring being disposed within said casing; a fixed contact secured to said casing and a movable contact carried by said contactor and engageable with said fixed contact; said contactor being operatively connected to said cam plate; said handle being engageable with said cam plate for movement of said contactor and said cam plate to positions wherein said main spring is effective to latch said contactor to said cam plate and to bring said contacts into engagement; said handle being engageable with said contactor for movement thereof to a position where-' in said main spring is effective to bring about the dis: engagement of said contacts; said main spring comprising a coiled element; seating means for said coiled element constructed and positioned whereby said coiled element is buckled at a point intermediate the ends thereof; said point being in engagement with said contactor whereby said contactor is urged to a stabilized position with re spect to said casing when said contacts are in engagement.

3. An electric switch comprising a casing, a cam plate, a contactor, an operating handle, and a main spring; said cam plate, said contactor, and said main spring being disposed within said casing; a fixed contact secured to said casing and a movable contact carried by said contactor and engageable with said fixed contact; said contactor being operatively connected to saidcamplate; said handle being engageablewith said cam plate for movement of said contactor and said: cam plate to positionsv wherein said main spring is effective: tov latch said contactor to saidcam plate and to bring said contactsintoengagement; said handle being engageable with said contactor for. movement thereof to a position wherein said main spring is efiective to bring about thedisengagement of said contacts; said main spring comprising a coiled element; said coiled element being buckled at a point intermediate the ends: thereof; said point being in engagement with said contactor whereby said contactor is urged to a stabilized position with respect to said casing when said contacts are in engagement; said coiled. member being seated at one end against an inclined formation of said casing and at the other end against said contactor.

4. An electric switch comprising acasing, a cam plate, a contactor, an operating handle, and a mainspring; said cam plate, said contactor, and said main spring being disposed within said casing; a fixed contact secured to said casing and amovable contact carried by said contactor and engageable with. said fixed contact; said contactor being oper'atively connected to saidcam plate; said handle being. engageable with said cam plate for movement of said contactor and said cam plate to positions wherein said main spring; is effective toilatch said, contactor to said cam plate and to bring said contacts into engagement; said. handle being engag able with said contactor for movement thereof to a position; wherein said main spring is effective to bring about the disengagement of said. contacts; said contactor including an L-shapedcontact arm having said movable contact: at the free end of a: first leg thereof; said main spring having one end thereof in contact with a, second leg of said contact arm anda second end thereof in contact with a seatformation of said casing; said seat formation comprising an inclined surface whereby said main spring is positioned to exert a component of force urging the junctionof said first and said second legs toward said camplate whereby said contactor assumes a predetermined position with respect to said cam plate when said contactor is latched thereto.

5'. An electric switch comprising a casing, a cam-plate, acontactor, an operating handle,,- and a main spring; said cam plate, said contactor, and said main spring being disposed within said casing; a fixed contact secured to said casing and a movable contact carried by said contactor and engageable with said fixed contact; said contactor being operatively connected to said cam plate; said handle being engageable with said cam plate for movement of said contactor and said cam plate to positions wherein said main spring is effective to latch said contactor to said cam plate and to bring said contacts into engagement; said handle being engageable with said contactor for movement thereof to a position wherein said main spring is effective to bring about the disengagement of said contacts; said contactor including an L-shaped contact arm having said movable contact at the free end of a first leg thereof; said main spring having one end thereof in contact with a second leg of said contact arm and a second end thereof in contact with a seat formation of said casing; said seat formation comprising an inclined surface whereby said mainspring is positioned to exert a component of force urging the junction of said first and said second legs toward said cam plate whereby said contactor assumes a predetermined position with respect to said cam plate when said contactor is latched thereto; said seat formation being formed integrally with said casing.

6. An electric switch comprising a casing, a cam plate, a contactor, an operating handle, and a main spring; said cam plate, said contactor, and said main spring being disposed within said casing; a fixed contact secured to said casing and a movable contact carried by said contactor and engageable with said fixed contact; said contactor being operatively connected to said cam plate; said handle being engageable with said cam plate for movement of said contactor and said cam plate to positions whereinsaid main spring is effective to latch said contactor to said cam plate and to bring said contacts into engagement; said handle being engageable with said contactor for movement thereof toa position wherein said main spring is effective to bring about the disengagernent-of said contacts; said contactor including an L-shaped contact arm having said movable contact at the free end of a first leg thereof; said main springhaving one end thereof in contact with a second leg of said contact arm and a second end thereof in contact-with a seat formation of said casing; said seat formation com prising an inclined surface whereby said main spring is positioned to exert a component of force urging the junction of said first and said second legs toward said cam plate whereby said contactor assumes a predetermined position with respect to said cam plate when said contactor is latched thereto; said seat formation comprising an insert member adapted to nest within a recess of said casing.

7. An electric switch comprising a casing, a cam plate, a contactor, an operating handle, and a main spring; said cam plate, said contactor, and said main spring being disposed within said casing; a fixed contact secured to said casing and a movable contact carried by said contactor and engageable with said fixed contact; said contactor being operatively connected to said cam plate; said handle being engageable with said cam plate for movement of said contactor and said cam plate to positions wherein said main spring is eifective to latch said contactor to said cam plate and to bring said contacts into engagement; said handle being engageable with said contactor for movement thereof to a position wherein said main spring is effective to bring about the disengagement of said contacts; said contactor also including a bimetallic element having a free end engageable with a latching edge of said cam plate for latching said contactor to said cam plate; said element being deformed, when heated to a predetermined temperature, to unlatch said contactor from said cam plate and permit said main spring to disengage said contacts independently of the position of said handle; seating means for said main spring constructed and positioned whereby said main spring is positioned to exert a component of force urging said contactor toward said cam plate to assume a predeterminable position with respect thereto when said con-' tactor is latched to said cam plate.

8. An electric switch comprising a casing, 21 cani plate, a contactor, an operating handle, and a main spring; said cam plate, said contactor, and said main spring being disposed within said casing; a fixed contact secured to said casing and a. movable contact carried by said contactor and engageable with said fixed contact; said contactor being operatively connected to said cam plate; said handle being engageable with said cam plate for movement of said contactor and said cam plate to positions wherein said main spring is effective to latch said contactor to said cam plate and to bring said contacts into engagement; said handle being engageable with said contactor for movement thereof to a position wherein said main spring is effective to bring about the disengagement of said contacts; said contactor also including a bimetallic element having a free end engageable with a latching edge of said cam plate for latching said contactor to said cam plate; said element being deformed, when heated to a predetermined temperature, to unlatch said contactor from said cam plate and permit said main spring to disengage said contacts independently of the position of said handle; said main spring being positioned to exert a component of force urging said contactor toward said cam plate to assume a predeterminable position with respect thereto when said contactor is latched to said cam plate; said contactor including an L-shaped contact arm having said movable contact at the free end of a first leg thereof; said main spring having one end thereof in contact with a seat formation of said casing; said seat formation comprising an inclined surface whereby said main spring is positioned to exert a component of force urging the junction of said first and said second legs toward said cam plate whereby said contactor assumes a predetermined position with respect to said cam plate when said contactor is latched thereto.

References Cited in the file of this patent UNITED STATES PATENTS 

